1. Field of the Invention
The invention pertains to the sealing of ducts through which pipes, cables, tubes or the like pass at the point where such elongate objects pass from such ducts into sewers, cable vaults, etc., to prevent the entry of water, gases, debris or other foreign objects from such ducts into such sewers, cable vaults, etc.
2. Description of the Prior Art
Duct seals commonly found in the prior art are sized to fit into a preset range of duct sizes and provide a set range of pipe, cable, etc., openings. Many seals are configured to handle multiple pipes, cables, etc., so that a seal can be placed about each pipe or cable, etc., passing therethrough. The outside diameter of the seal exceeds the inside diameter of the duct so that the seal is slightly compressed as it is installed. Also the pipe, cable, etc., apertures are slightly undersized to be expanded by the pipe or cable and thus tightly seal thereabout. To provide the needed ranges of duct size, pipe or cable number, etc., requires that a large number of seals be available.
To decrease the number of seal sizes which must be inventoried, a seal or plug assembly 10 as is shown in U.S. Pat. No. 4,622,436 issued Nov. 11, 1986, and owned by the assignee of the instant invention, may be employed. Two or more ring members 18, 24 are sandwiched between compression members 36, 38 operated by biasing means 52, 54. The plug assembly 10 is positioned in a conduit 14 and the cables 12b, 12c and 12a are passed through corresponding apertures 18a, 18b, 18c and 24a, 24b, 24c (see FIG. 2 of the patent). The plug ring members 18, 24 are then expanded by compression members 36, 38 to grip the cables 12a, 12b, 12c and the inner surface of conduit 14. Despite the fact that the expansion of the ring members 18 and 24 permits each size of plug assembly 10 to cover a greater range of duct/cable size, the need for the rigid compression members 36 and 38 limits the applicability of the device especially where the pipe or cable, etc., is of a diameter close to the inside diameter of the duct.